The present study is aimed at a precise understanding of possible abnormal immune regulation in patients with various human disease states including acute rheumatic fever, disseminated lupus erythematosus, and rheumatoid arthritis. Studies are now being specifically directed at changes in lymphocyte cell surface markers including alterations in human Ia atigens expressed on many human B cells as well as a small fraction of human T cells. Binding of human C-reactive protein is being examined for possible lymphocyte subpopulation specificity.